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Chem 2425

30 Questions
Chem 2425
Questions and Answers
  • 1. 
    1. If 50.0 g of benzene, C6H6, at 25.00C absorbs 2.71 kJ of energy in the form of heat, what is the final temperature of the benzene? The specific heat of benzene is 1.72 J/g·0C.
    • A. 

      25.00C

    • B. 

      31.50C

    • C. 

      56.50C

    • D. 

      32.30C

    • E. 

      57.30C

  • 2. 
    2. If 495 J is required to change the temperature of 12.7 g of sodium chloride from 75.00C to 135 0C, what is the specific heat of sodium chloride?
    • A. 

      0.866 J/g·0C

    • B. 

      2.60 J/g·0C

    • C. 

      0.650 J/g·0C

    • D. 

      1.15 J/g·0C

    • E. 

      2.83 × 105 J/g·0C

  • 3. 
    3. Water has a specific heat of 4.18 J/g · 0C. If 35.0 g of water at 98.8 0C loses 4.94 kJ of heat, what is the final temperature of the water?
    • A. 

      32.00C

    • B. 

      46.20C

    • C. 

      47.20C

    • D. 

      57.20C

    • E. 

      65.0C

  • 4. 
    4. When 66.0 g of an unknown metal at 28.50C is placed in 83.0 g H2O at 78.50C, the water temperature decreases to 75.90C. What is the specific heat capacity of the metal? The specific heat capacity of water is 4.184 J/g0C.
    • A. 

      0.055 J/g· 0C

    • B. 

      0.29 J/g · 0C

    • C. 

      0.69 J/g · 0C

    • D. 

      0.18 J/g · 0C

    • E. 

      2.6 J/g · 0C

  • 5. 
    5. A coffee-cup calorimeter contains 10.0 g of water at 59.000C. If 3.00 g gold at 15.20 0C is placed in the calorimeter, what is the final temperature of the water in the calorimeter? The specific heat of water is 4.18 J/g ·0C; the specific heat of gold is 0.128 J/g ·0C.
    • A. 

      55.37 C

    • B. 

      58.60 C

    • C. 

      59.40 C

    • D. 

      60.80 C

    • E. 

      64.19 C

  • 6. 
    6. When 10.0 g KOH is dissolved in 100.0 g of water in a coffee-cup calorimeter, the temperature rises from 25.18 0C to 47.53 0C. What is the enthalpy change per gram of KOH dissolved in the water? Assume that the solution has a specific heat capacity of 4.18 J/g0C.
    • A. 

      –116 J/g

    • B. 

      –934 J/g

    • C. 

      –1.03 × 103 J/g

    • D. 

      –2.19 × 103 J/g

    • E. 

      –1.03 × 104 J/g

  • 7. 
    7. 10.0 g of ice at 0.00 0C is mixed with 25.0 g of water at 35.000C in a coffee-cup calorimeter. What is the final temperature of the mixture? The specific heat of water is 4.18 J/g 0C; the heat of fusion of water is 333 J/g.
    • A. 

      0.00 0C

    • B. 

      2.24 0C

    • C. 

      5.22 0C

    • D. 

      25.0 0C

    • E. 

      47.8 0C

  • 8. 
    8. All of the following statements are true EXCEPT
    • A. 

      Hess' law states that ΔH for an overall reaction is the sum of the ΔH values for the individual equations.

    • B. 

      The molar enthalpy of formation of a compound is equal to the enthalpy change when one mole of the compound is formed from elements.

    • C. 

      A reaction with a negative enthalpy is exothermic.

    • D. 

      The enthalpy of formation of an element in its most stable state is equal to zero.

    • E. 

      The sum of the enthalpies of formation of the products in a chemical reaction is defined as the enthalpy of reaction.

  • 9. 
    9. Determine the heat of reaction for the combustion of ammonia,         4NH3(g) + 7O2(g) → 4NO2(g) + 6H2O(l) using molar enthalpies of formation. NH3(g)    –45.9 NO2(g)    +33.1 H2O(l)    –285.8
    • A. 

      +30.24 kJ

    • B. 

      –206.9 kJ

    • C. 

      –298.6 kJ

    • D. 

      –1398.8 kJ

    • E. 

      –1663.6 kJ

  • 10. 
    10. The standard molar enthalpy of formation of NH3(g) is –45.9 kJ/mol. What is the enthalpy change if 9.51 g N2(g) and 1.96 g H2(g) react to produce NH3(g)?
    • A. 

      –10.3 kJ

    • B. 

      –20.7 kJ

    • C. 

      –29.8 kJ

    • D. 

      –43.7 kJ

    • E. 

      –65.6 kJ

  • 11. 
    11. For the reaction below relate the rate of disappearance of hydrogen to the rate of formation of ammonia.         N2(g) + 3H2(g) → 2NH3(g)
    • A. 

      A: +

    • B. 

      B: 3

    • C. 

      C: 1/2

    • D. 

      D: -1/3

    • E. 

      E: -

  • 12. 
    12. The rate of reaction for the formation of carbon monoxide is measured at 1.24 mol/L·hr. What is the rate of formation of carbon monoxide in units of mol/L·s?         CH3CHO(g) → CH4(g) + CO(g)
    • A. 

      3.44 × 10-4 mol/L·s

    • B. 

      2.07 × 102 mol/L·s

    • C. 

      1.24 mol/L·s

    • D. 

      74.4 mol/L·s

    • E. 

      4.64 × 103 mol/L·s

  • 13. 
    13. For the reaction below, if the rate of appearance of Br2 is 0.180 mol/L·s, what is the rate of disappearance of NOBr?         2NOBr(g) → 2NO(g) + Br2(g)
    • A. 

      –0.360 mol/L·s

    • B. 

      –0.090 mol/L·s

    • C. 

      0.090 mol/L·s

    • D. 

      0.180 mol/L·s

    • E. 

      0.360 mol/L·s

  • 14. 
    14. Dinitrogen pentaoxide decomposes to nitrogen dioxide and oxygen according to the following balanced chemical equation and rate expression.         2N2O5(g) → 4NO2(g) + O2(g)         rate = k[N2O5] What is the overall reaction order?
    • A. 

      0

    • B. 

      1

    • C. 

      2

    • D. 

      5

    • E. 

      7

  • 15. 
    The initial rates method was used to study the reaction below.         A + 3B =2C     [A] (mol/L)    [B] (mol/L)   -D[A]/Dt (mol/L×s)     0.210        0.150         3.41 x 10^3     0.210        0.300        1.36 x 10^2     0.420        0.300        2.73 x 10^-2
    • A. 

      Rate = 0.515[A] x [B]

    • B. 

      Rate = 0.515[A]^2 x [B]

    • C. 

      Rate = 0.721[A]^2 x [B]

    • D. 

      Rate = 0.721[A] x [B]^2

    • E. 

      Rate = 0.721[A]^2 x [B]^2

  • 16. 
    16. The initial rates method was used to study the reaction below.         2A + B + C → D + E
      [A] (mol/L) [B] (mol/L) [C] (mol/L) Δ[D]/Δt (mol/L·s)
      0.150 0.250 0.300 1.47 × 106
      0.150 0.125 0.300 3.68 × 107
      0.150 0.250 0.600 2.94 × 106
      0.300 0.125 0.300 7.35 × 107
     
    • A. 

      Rate = 8.71 × 104[A]2 × [B] × [C]

    • B. 

      Rate = 5.23 × 104[A] × [B]2 × [C]

    • C. 

      Rate = 2.90 × 103[A]2 × [B] × [C]2

    • D. 

      Rate = 8.71 × 104[A] × [B] × [C]2

  • 17. 
    • A. 

      8.72 × 105 M

    • B. 

      0.0645 M

    • C. 

      0.115 M

    • D. 

      0.0785 M

    • E. 

      0.643 M

  • 18. 
    18. The rate constant for the decomposition of cyclobutane is 2.08 × 10-2 s-1 at high temperatures.         C4H8(g) → 2C2H4(g) How many seconds are required for an initial concentration of 0.100 M C4H8(g) to decrease to 0.0450 M?
    • A. 

      0.00114 s

    • B. 

      1.07 s

    • C. 

      2.64 s

    • D. 

      38.4 s

    • E. 

      874 s

  • 19. 
    • A. 

      0.0050 M

    • B. 

      0.051 M

    • C. 

      0.51 M

    • D. 

      0.11 M

    • E. 

      2.0 × 102 M

  • 20. 
    20. For the first-order reaction below, the concentration of product B after 24.2 seconds is 0.322 M. If k = 8.75 × 10-2 s-1, what was the initial concentration of A?
      A → 2B  rate = k[A]
    • A. 

      0.0341 M

    • B. 

      0.183 M

    • C. 

      1.34 M

    • D. 

      2.68 M

    • E. 

      29.3 M

  • 21. 
    21. For the second-order reaction below, the rate constant of the reaction is 9.4 × 10–3 M–1s–1. How long (in seconds) is required to decrease the concentration of A from 2.16 M to 0.40 M?
      2A → B rate = k[A]2
     
    • A. 

      2.0 × 10^1 s

    • B. 

      7.8 × 10^1 s

    • C. 

      1.8 × 10^2 s

    • D. 

      1.9 × 10^2 s

    • E. 

      2.2 × 10^2 s

  • 22. 
    22. For the first-order reaction below, the initial concentration of A is 0.80 M. What is the half-life of the reaction if the concentration of A decreases to 0.10 M in 54 seconds?
      A → B rate = k[A]
     
    • A. 

      18 s

    • B. 

      24 s

    • C. 

      36 s

    • D. 

      48 s

    • E. 

      51 s

  • 23. 
    • A. 

      1 only

    • B. 

      2 only

    • C. 

      3 only

    • D. 

      2 and 3

    • E. 

      1, 2, and 3

  • 24. 
    What is the correct equilibrium constant expression for the following reaction?         CO2(g) + 2H2O(g)  CH4(g) + 2O2(g) a.                  b.                  c.              d.        
    • A. 

      A

    • B. 

      B

    • C. 

      C

    • D. 

      D

  • 25. 
    25. Write a balanced chemical equation which corresponds to the following equilibrium constant expression.        
    • A. 

      1/2N2(g) + 3/2H2(g) = NH3(g)

    • B. 

      N2(g) + 3 H2(g) = 2NH3(g)

    • C. 

      2NH3(g) = N2(g) + 3H2(g)

    • D. 

      NH3(g) = 1/2N2(g) + 3/2H2(g)

    • E. 

      2N2(g) + 6H2(g) = 4NH3(g)

  • 26. 
    Use the equilibrium constants for the following reactions at 700 0C
      2SO2(g) + O2(g)  2SO3(g) K1 = 4.8
      2NO(g) + O2(g)  2NO2(g) K2 = 16
    to determine the equilibrium constant for the following reaction.         SO3(g) + NO(g)  SO2(g) + NO2(g)
    • A. 

      0.30

    • B. 

      0.55

    • C. 

      0.85

    • D. 

      1.8

    • E. 

      3.3

  • 27. 
    • A. 

      0.00153

    • B. 

      0.00308

    • C. 

      0.00611

    • D. 

      0.00730

    • E. 

      0.02471

  • 28. 
    28. For the system         CO(g) + H2O(g)  CO2(g) + H2(g) K is 1.6 at 900 K. If 0.400 atm CO(g) and 0.400 atm H2O(g) are combined in a sealed flask, what is the equilibrium partial pressure of CO2(g)?
    • A. 

      0.22 atm

    • B. 

      0.31 atm

    • C. 

      0.47 atm

    • D. 

      0.47 atm

    • E. 

      0.65 atm

  • 29. 
    29. Which of the following may change the ratio of products to reactants in an equilibrium mixture for a chemical reaction involving gaseous species?     1.    Increasing the temperature.     2.    Adding a catalyst.     3.    Adding gaseous reactants.
    • A. 

      1 only

    • B. 

      2 only

    • C. 

      3 only

    • D. 

      1 and 2

    • E. 

      1 and 3

  • 30. 
    Calcium carbonate decomposes to calcium oxide and carbon dioxide.
      CaCO3(s)   CaO(s) + CO2(g) ΔH0 = 179 kJ
    The equilibrium constant for this reaction is 9.7 × 1024 at 298 K. What is the equilibrium constant at 575 K? (R = 8.31 J/mol·K)
    • A. 

      7.5 × 10^-16

    • B. 

      1.3 × 10^-8

    • C. 

      1.4 × 10^-38

    • D. 

      1.3 × 10^-15

    • E. 

      1.0 * 10^-23

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